System for suppressing cavitation in a hydraulic component

ABSTRACT

A system is provided for suppressing flow-induced cavitation in a fluid  f. At least one acoustic transducer is coupled to the fluid flow in a region that is susceptible to the formation of cavitation bubbles. The transducer (or transducers) applies an acoustic field to the fluid flow in order to raise the cavitation threshold pressure of the fluid flow above the total local pressure including the pressure drop induced by the fluid flow and the pressure due to the acoustic field.

This application is a division of application Ser. No. 08/807,128 filedFeb. 26, 1997, now U.S. Pat. No. 5,884,650.

STATEMENT OF GOVERNMENT INTEREST

The invention described herein may be manufactured and used by or forthe Government of the United States of America for Governmental purposeswithout the payment of any royalties thereon or therefor.

BACKGROUND OF THE INVENTION

(1) Field of the Invention

The present invention relates generally to suppressing cavitation in ahydraulic component, and more particularly to a system using acousticenergy to suppress cavitation in a hydraulic component.

(2) Description of the Prior Art

Cavitation in and near hydraulic components (e.g., valves, pumps,injectors, conduits with sharp bends, etc.) of a fluid flow system isundesirable for a variety of reasons. The formation of cavitationbubbles adversely affects the performance of the system. The largerelease of heat energy brought about by the contraction and collapse ofa vapor bubble can cause pitting on the inside surfaces of the hydrauliccomponent. Over time, the pitting can affect the fluid flow and/or leadto failure of the hydraulic component. In addition, the formation andsubsequent collapse of cavitation bubbles generates acoustic noisewithin the system.

Prior art approaches to preventing cavitation involve particularmechanical designs of the hydraulic component. This generally requirescomplete replacement of parts in an already existing fluid flow system.However, such replacement is not always practical or cost effective. Inaddition, specific mechanical designs might not be able to preventcavitation in the event of changing flow conditions (e.g., pressurechanges in the fluid flow due to velocity changes).

SUMMARY OF THE INVENTION

Accordingly, it is an object of the present invention to provide asystem for preventing cavitation in or near a hydraulic component.

Another object of the present invention is to provide a system forpreventing cavitation in or near a hydraulic component of an existingfluid-flow system without changing any mechanical components thereof.

Still another object of the present invention is to provide a system forpreventing cavitation in or near a hydraulic component that adapts tochanging flow conditions.

Other objects and advantages of the present invention will become moreobvious hereinafter in the specification and drawings.

In accordance with the present invention, a system is provided forsuppressing flow-induced cavitation in a fluid flow through a hydrauliccomponent. At least one acoustic transducer is coupled to the fluid flowin a region of the hydraulic component that is susceptible to theformation of cavitation bubbles. The transducer (or transducers) appliesan acoustic field to the fluid flow in order to raise the cavitationthreshold pressure above the total local pressure including the pressuredrop induced by the fluid flow and the local acoustic field. Since thecavitation pressure is above the total local pressure in the fluid flow,cavitation bubbles are prevented from forming. The hydraulic componentsdo not require replacement with any specially designed components as thetransducer can be affixed to the exterior of the components and theacoustic field directed through the component into the fluid flow. Wherethe acoustic field cannot be transferred through the hydrauliccomponent, the transducer may be placed within the component itself. Thesystem can also include the sensing of conditions of the fluid flowrelated to the formation of cavitation bubbles. Such conditions caninclude the acoustic noise associated with the formation of cavitationbubbles. The same (or different) transducer can be used to detect thisacoustic noise. The acoustic field applied by the transducer can then bevaried to adapt to the changing flow environment and to maintaincavitation suppression.

BRIEF DESCRIPTION OF THE DRAWINGS

Other objects, features and advantages of the present invention willbecome apparent upon reference to the following description of thepreferred embodiments and to the drawings, wherein correspondingreference characters indicate corresponding parts throughout the severalviews of the drawings and wherein:

FIG. 1 is a schematic view of a hydraulic component with an acoustictransducer provided to suppress cavitation in accordance with the systemof the present invention;

FIG. 2 is a logarithmic plot depicting, in general, the cavitationthreshold curve as a function of frequency;

FIG. 3 is a schematic view of an embodiment that uses an acoustictransducer to both sense conditions related to cavitation and tosuppress cavitation in accordance with the present invention; and

FIG. 4 is a schematic view of another embodiment that uses a pluralityof acoustic transducers, some of which are dedicated to sense conditionsrelated to cavitation and some of which are dedicated to suppresscavitation in accordance with the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT(S)

Referring now to the drawings, and more particularly to FIG. 1, thebasics of the present invention will be explained. A hydrauliccomponent, e.g., conduit 10, is shown with a fluid flow passingtherethrough as represented by arrows 12. It is to be understood thatconduit 10 is representative of any hydraulic component through which afluid can pass. An acoustic transducer 14 is disposed so as to transferacoustic energy to fluid flow 12 and is coupled to an AC source 16 forexcitation thereof. Transducer 14 can be placed on the exterior ofconduit 10 provided conduit 10 can transfer acoustic waves therethroughto fluid flow 12. Otherwise, transducer 14 can be placed within conduit10 for direct coupling to fluid flow 12. For purpose of illustration,only one transducer 14 is shown. However, it is to be understood that aplurality of such acoustic transducers can be used, each of which couldbe excited by the same AC source 16 or by different AC sources.

Flow-induced cavitation suppression in the present invention isaccomplished as follows. As fluid flow 12 passes through medium 10, ACsource 16 excites acoustic transducer 14 to create a high-amplitudeacoustic field in fluid flow 12. The acoustic field applied bytransducer 14 must raise the cavitation threshold pressure above thetotal pressure within fluid flow 12 in the region of conduit 10 wheretransducer 14 is located. In other words, the total pressure withinfluid flow 12, i.e., ambient pressure minus the pressure drop due tofluid flow 12 plus the acoustic pressure applied by transducer 14, mustbe less than the cavitation threshold pressure. In general, cavitationthreshold pressure increases as a function of frequency as shown bycurve 100 in FIG. 2 which is a logarithmic plot of cavitation thresholdpressure versus frequency. Thus, once the specifics of curve 100 areknown for a particular hydraulic component: (e.g., conduit 10) and fluidflow 12, transducer 14 is driven to maintain operation below curve 100.

To adapt to changing flow conditions, the system of the presentinvention can be implemented as shown in FIG. 3. Transducer 14 isswitched between AC source 16 and receiver circuit 18 via switch control20. In operation, switch control 20 would initially couple transducer 14to receiver circuit 18 so that transducer 14 operates as an acousticreceiver. In this mode of operation, transducer 14 would sense acousticconditions within fluid flow 12. Since the onset of cavitation producesnoise, transducer 14 is thus set to detect such noise. At a thresholdlevel of noise indicative of cavitation, receiver circuit 18 sends acontrol signal to switch control 20 to cause transducer 14 to be coupledto AC source 16. In this way, transducer 14 now operates as atransmitter to apply an acoustic field to fluid flow 12 in order toraise the cavitation threshold as described above. After a set period oftime, switch control 20 can once again couple transducer 14 to receivercircuit 18 in order to determine if cavitation is continuing or if ithas been suppressed. Should cavitation continue, the frequency of ACsource 16 can be increased in accordance with a pre-set or adaptivescheme.

Another alternative is for switch control 20 to automatically andperiodically switch transducer 14 between its receiver and transmittermodes of operation. If operation proceeded in this fashion, receivercircuit 18 would provide an activation signal (represented by dashedline 22) to AC source 16 indicating the presence of cavitation in fluidflow 12. In this way, excitation of transducer 14 as a transmitter wouldonly occur when both switch control 20 coupled AC source 16 totransducer 14 and activation signal 22 was present. Once again, thefrequency of AC source 16 can be increased in accordance with a pre-setor adaptive scheme until cavitation ceases.

Since it may be desirable to continually monitor acoustic conditionswithin fluid flow 12, the system of the present invention can bepracticed using the embodiment depicted in FIG. 4. One or more acoustictransducers 14A are operated as dedicated receivers and are therefordirectly and continually coupled to receiver circuit 18. One or moreacoustic transducers 14B are operated as dedicated transmitters and aretherefore directly coupled to AC source 16. In operation, receivercircuit 18 supplies activation signal 22 to switch control 20 only whenacoustic noise associated with cavitation in fluid flow 12 is detectedby transducers 14A. Thus, transducers 14B are only activated whencavitation commences. When activation signal 22 is no longer present,i.e., cavitation has ceased, transducers 14B are inactive.

The advantages of the present invention are numerous. The flow-inducedcavitation suppression system can be implemented on new or existingfluid flow systems. The system adapts to changing flow conditions and istherefore more versatile then conventional mechanical "fixes". Sincethere are no mechanical components, this system of flow-inducedcavitation suppression is robust. Further, since it will generally notbe necessary to introduce any of the system components into the fluidflow, the system of the present invention should have no negative impacton the fluid flow.

It will be understood that many additional changes in the details,materials and arrangement of parts, which have been herein described andillustrated in order to explain the nature of the invention, may be madeby those skilled in the art within the principle and scope of theinvention as expressed in the appended claims.

What is claimed is:
 1. A system for suppressing flow-induced cavitationin a fluid flow through a hydraulic component, comprising:at least oneacoustic transducer coupled to said fluid flow in a region of saidhydraulic component for generating an acoustic signal in response to theformation of cavitation bubbles in said fluid flow; a receiver circuitcoupled to said at least one acoustic transducer for generating acontrol signal in response to said acoustic signal; an AC source; and aswitch control coupled to said AC source and said receiver circuit forcoupling said AC source to said at least one acoustic transducer inresponse to said control signal, wherein an acoustic field is applied tosaid fluid flow in said region by said at least one acoustic transducercoupled to said AC source.
 2. A system as in claim 1 wherein:said atleast one acoustic transducer comprises a single acoustic transducer;said receiver circuit is coupled to said single acoustic transducer foroperating said single acoustic transducer as a receiver when coupledthereto for sensing conditions related to the formation of saidcavitation bubbles; and said switch control uncouples said singleacoustic transducer from said receiver circuit and couples said singleacoustic transducer to said AC source.
 3. A system as in claim 1wherein:said at least one acoustic transducer comprises a plurality ofacoustic transducers; said receiver circuit is coupled to at least oneof said plurality of acoustic transducers for operating said at leastone of said plurality of acoustic transducers as an acoustic receiver toacoustically sense the formation of said cavitation bubbles in saidregion; and said switch control couples others of said plurality ofacoustic transducers to said AC source when said at least one of saidplurality of acoustic transducers operating as an acoustic receiveracoustically senses the formation of said cavitation bubbles in saidregion, said acoustic field being applied to said fluid flow in saidregion by said others of said plurality of acoustic transducers.
 4. Asystem as in claim 1 wherein said AC source is a variable frequencysource.
 5. A system for suppressing flow-induced cavitation in a fluidflow through a hydraulic component, comprising:at least one acoustictransducer coupled to said fluid flow in a region of said hydrauliccomponent; and means for operating said at least one acoustic transduceras a receiver until conditions related to the formation of cavitationbubbles are detected in said region, and for operating said at least oneacoustic transducer as a transmitter to apply an acoustic field to saidfluid flow in said region once said conditions related to the formationof said cavitation bubbles are detected.
 6. A system as in claim 5,wherein said at least one acoustic transducer comprises a singleacoustic transducer.
 7. A system as in claim 5, wherein:said at leastone acoustic transducer comprises a plurality of acoustic transducers;said means operates at least one of said plurality of acoustictransducers as said receiver to acoustically sense the formation of saidcavitation bubbles in said region; and said means operates others ofsaid plurality of acoustic transducers as said transmitter when said atleast one of said plurality of acoustic transducers operating as saidreceiver acoustically senses the formation of said cavitation bubbles insaid region, said acoustic field being applied to said fluid flow insaid region by said others of said plurality of acoustic transducers. 8.A system as in claim 7, wherein said means continuously operates said atleast one of said plurality of acoustic transducers as said receiver.